<div>
    <h4>this is book</h4>
    <p>
        <button ng-click="bookService()" class="btn btn-primary">bookService</button>
    </p>
    result:
    <ul class="list-group">
        <li ng-repeat="(key, value) in books" class="list-group-item">
            <label>{{value}}</label>
        </li>
    </ul>
</div>
